Centrifugal clutch



g- 29, 1967 s. J. HOFF CENTRIFUGAL CLUTCH Filed Nov. 29, 1965 //VVEN TO/E.

/ ATTORNEYS United States Patent 3,338,361 CENTRIFUGAL CLUTCH Stephen J. Hoff, Richmond, Ind., assignor to Hotfco, Inc., Richmond, Ind., a corporation of Indiana Filed Nov. 29, 1965, Ser. No. 510,282 6 Claims. (Cl. 192-105) This invention relates to a centrifugal clutch of the type shown in my prior Patent No. 3,026,980 in which centrifugal clutch shoes having a controlled self-energizing action are mounted on a shoe carrier.

It is the object of the present invention to simplify and improve the construction of such clutches, to reduce the number of parts and the machine operations required, and to provide an improved and more compact clutch with equal or better function.

Clutches embodying the present invention may be adapted for one-directional operation but preferably are arranged for operation in either direction of rotation and are therefore symmetrical with respect to a central plane. The preferred clutch comprises a pair of clutch shoes mounted on a carrier and centrifugally movable against a surrounding clutch drum. The carrier provides two pairs of cam reaction bosses, each formed to engage both a main cam face and a control cam face on its associated shoe. Each shoe has an outer friction face curved to engage the drum, and an inner face which is generally chordal and, the end portions of which form main cams to operate against the reaction boss at the trailing end of the shoe. Each shoe also has end portions standing inward from the chordal inner surface which define inner control-cam faces to operate against the reaction boss at the leading end of the shoe. Each shoe thus straddles a pair of reaction bosses and seats downward and inward against each boss. The shoes are biased to seated, retracted position by springs stretched between them at their ends, which preferably act generally in the direction of the control-cam faces. When a shoe moves outward under centrifugal force into engagement with the drum, it also moves rearward and the main cam tends to wedge it outward against the drum. The control cam at the lead ing end of the shoe is shaped to control such rearward movement in substantially direct response to the action of the adjacent spring. A controlled self-energizing action is thereby produced which gives smooth and positive engagement, as well as positive release when centrifugal force falls below the spring force.

In accordance with the present invention, the engaging surfaces of the shoe cams and their reaction bosses are made to extend axially a substantial distance, preferably the full width of the shoe, and are thereby made to position and stabilize the shoe in upright, radial-plane position on the carrier, against tipping or twisting relative to the carrier. The carrier is preferably made as a single integral body having a central hub and two pairs of camreaction bosses projecting therefrom; and each. shoe stabilized upright on the bosses is held against axial displacement on the carrier by means of a small disk extending between facing radial-plane slots in the inner face of the shoe and the peripheral face of the carrier. The interengagement of the slot and disk is made of sufficient depth to hold the shoe against axial displacement in all operating positions, and with sufiicient clearance to permit operative shoe movement.

The accompanying drawing illustrates the invention. In such drawing,

FIG. 1 is an axial section of a clutch assembly embodying the present invention, taken on the line 1-1 of FIG. 2;

FIG. 2 is a section taken on the line 2-2 of FIG. 1, with the shoes in seated, retracted position;

FIG. 3 is a section similar to FIG. 2 but showing the shoes in drum-engaging position; and

FIG. 4 is a section taken on the line 4-4 of FIG. 2.

The clutch shown in the drawing is mounted on a shaft 10 and is arranged to drive a drum 12 carried by a chain sprocket 14 rotatably supported by a roller bearing 16 on the reduced end of the shaft 10. A nut on the end of the shaft10 supports a chain guard 18 and holds the assembly together against a shoulder on the shaft 10. The drum 12 and sprocket 14 form the driven half of the clutch.

The driving half of the clutch comprises a carrier 20 mounted on the shaft 10 and keyed thereto by a key 22. The carrier 20 has a central hub of generally cylindrical configuration, and two pairs'of radially projecting camreaction bosses 24 and 26, the ends of which are defined by semi-cylindrical surfaces extending axially parallel to the shaft 10. Each pair of bosses 24 and 26 supports and is straddled by a clutch shoe 28 which has an outer friction face 30 of a cylindrical configuration to engage the drum 12. The inner face of each shoe is generally chordal and its ends form main cam faces 32 bearing against the bosses 24 and 26 in a direction parallel to the central plane of symmetry indicated by the line 1-1 in FIG. 2. Outward of such cam faces 32, each shoe has end portions 34 standing inward from the cam faces 32 and defining inner cam faces 36 at an angle slightly larger than a right angle to the cam face 32, preferably an angle on the order of 105 in the structure shown. These cam faces 36 are positioned to bear against the outer ends of the cam reaction bosses 24 and 26 to act as control cams in the operation of the clutch.

The semi-cylindrical end faces of the bosses 24 and the cam faces 32 and 36 which bear against such bosses all extend axially of the clutch for a considerable distance, preferably the full width of the clutch carrier and shoes, as indicated in the FIG. 4; and in the normal operation of the clutch both such cam faces of each shoe are continuously in engagement with the pair of bosses 24 or 26 supporting the shoe, and this engagement holds the shoe stable in upright radial-plane position on the carrier 20 under all conditions of operation.

' To prevent axial displacement of the thus stabilized shoe on the carrier 20, the inner face of each shoe and the underlying periphery of the carrier are provided with facing radial-plane slots 38 and 40, and a disk 42 is placed in each facing pair of slots. The disk is large enough to engage both slots in all operative positions of the shoes relative to the carrier 20 and has sufiicient radial and side clearance to permit free movement of the shoes in their operation.

Each end of each shoe 28, outside the end portion 34, carries a tongue 44 provided with a hole for the reception of the hooked end of a tension spring. The two shoes 28 are biased to retracted position, and against the cam-reaction bosses 24 by springs stretched between the tongues 44 at the ends of the shoes. The springs extend and act in substantially the direction of the cam faces 36.

The carrier 20, the two shoes 28, the two disks 42, and the two springs 46 form a self-contained assembly which can be mounted as such on a shaft such as the shaft 10, and the shoes require no lateral support such as that provided by the side plates of the clutch shown in my prior Patent No. 3,026,980. Since the carrier 20 is preferably a one-piece part entirely defined by axial surfaces, it can readily be formed to provide a highly accurate configuration and position of its cam reaction bosses 24 and their shoe-engaging faces, so that the shoes can be accurately located and will be held true in all conditions of operation. The disks 42 in the readilyformed slots 38 and 40 adequately locate and maintain the shoes in proper axial position on the carrier 20 and greatly reduce the cost and complexity of the clutch assembly.

The operation of the clutch is indicated in FIG. 3, where shaft rotation is clockwise. As a rotary shoe 28 is movedoutward by centrifugal force into engagement I trailing-end boss 24. The movement of the trailing end of the shoe is relatively small and the camming action produced by the main cam 32 tends to wedge the shoe 28 between the boss and the drum 12.

At the forward or leading end of the shoe 28, a different action occurs. The control-cam face 36 at such leading end of the shoe remains in engagement with the underlying boss 24 while the main cam face 32 becomes inoperative and moves away from the boss 24. The inclination of the control cam face 36 regulates the rear- 7 ward movement of the shoe at its trailing end and regulates the wedging action produced by the main cam 32 at that trailing end. The movement of the leading end of the shoe 28 relative to the underlying boss 24 is relative ly large, as shown in FIG. 3. Moreover, such movement is substantially in the direction of action of the spring 46 and is thus directly controlled by that spring 46. As a result, the engaging and disengaging action of each shoe in response to centrifugal force is directly and positively controlled by the spring 46 at the leading end of the shoe in cooperation with the action of the two control cams 36 extending in substantially the same direction.

The action maintains both ends of each shoe is continuous engagement, on axial surfaces, with spaced camreaction bosses, and such engagement cooperates with the central radial-plane disks and slots to maintain the carrier and shoe assembly together as a self-contained,

operating unit.

I claim:

1. A centrifugal clutch, comprising a shoe carrier adapted to be mounted for rotation on an axis and formed with chordally-spaced, outwardly-presented, cam-reaction, shoe-supporting surfaces,

a clutch shoe having an outer arcuate drum-engaging face and extending between and across said shoesupporting surfaces, and being biased into engagement with such surfaces,

the engaging surfaces between said carrier and shoe being axially-extending surfaces of sufficient extent to maintain the shoe in upright radial-plane position on the carrier and being disposed to prevent circumferential displacement of the shoe from opera- 55 tive position relative to the carrier,

said shoe and carrier being provided with facing, aligned, radial-plane slots of a depth greater than the normal operative movement of the shoe relative to the carrier, and

a flat keeper-plate housed in said slots and extending between the shoe and carrier slots to maintain said slots coplanar and said shoe against axial displacement along said axial-extending surfaces.

2. A centrifugal clutch according to claim 1, in which said shoe has an inner main-cam face adjacent its trailing end in engagement with the cam-reaction surface at such trailing end, and a control-cam face adjacent its leading end,

said main-cam face being disposed to converge with said drum-engaging face in a rearward direction of said shoe to drum engagement tending to force the main cam face against its supporting reaction surface with a wedging action,

said control-cam face being disposed and positioned to remain in engagement with the cam reaction surface at the leading end of the shoe and to control the wedging action at the main cam, the shoe being thereby maintained in supported engagement with said axially-extending shoe-supporting surfaces throughout its operating movements,

said slots and keeper plate being disposed between said cams and supporting surfaces at the leading and trailing ends of the shoe.

3. A centrifugal clutch according to claim 2 in which said cam reaction surfaces are symmetrical about a central axial plane,

said shoe has symmetrical main-cam and control-cam faces at both ends,

said slots are arcuate slots, and

said keeper plate is a flat circular disk.

4. A centrifugal clutch according to claim 1, adapted for operation in either direction of rotation, in which said shoe has main-cam and control-cam faces at both ends, with each control-cam face extending inward from the outer end of the main-cam face,

said chordally-spaced cam-reaction surfaces are straddled by said shoe and include portions which substantially engage both the main-cam and controlcam faces at both ends of the shoe when the shoe is in retracted position, to center the shoe on its supporting surfaces, and

said slots are located between said main-cam faces, in

the central radial plane of the shoe,

5. A centrifugal clutch according to claim 1 in which said slots are arcuate slots and said keeper plate is a flat circular disk.

6. A centrifugal clutch according to claim 4 in which said slots are arcuate slots and said keeper plate is a flat circular disk.

References Cited UNITED STATES PATENTS 2,224,935 12/ 1940 Schultz 192105 X 2,756,856 7/1956 Dudley 192-105 3,026,980 3/1962 Hoff l92105 BENJAMIN W. WYCHE III, Primary Examiner. 

1. A CENTRIFUGAL CLUTCH, COMPRISING A SHOE CARRIER ADATPED TO BE MOUNTED FOR ROTATION ON AN AXIS AND FORMED WITH CHORDALLY-SPACED, OUTWARDLY-PRESENTED, CAM-REACTION, SHOE-SUPPORTING SURFACES A CLUTCH SHOE HAVING AN OUTER ARCUATE DRUM-ENGAGING FACE AND EXTENDING BETWEEN AND A CROSS SAID SHOESUPPORTING SURFACES, AND BEING BIASED INTO ENGAGEMENT WITH SUCH SURFACES, THE ENGAGING SURFACES BETWEEN SAID CARRIER AND SHOE BEING AXIALLY-EXTENDING SURFACES OF SUFFICIENT EXTENT TO MAINTAIN THE SHOE IN UPRIGHT RADIAL-PLANE POSITION ON THE CARRIER AND BEING DISPOSED TO PREVENT CIRCUMFERENTIAL DISPLACEMENT OF THE SHOE FROM OPERATIVE POSITION RELATIVE TO THE CARRIER, SAID SHOE AND CARRIER BEING PROVIDED WITH FACING, ALIGNED, RADIAL-PLANE SLOTS OF A DEPTH GREATER THAN THE NORMAL OPERATIVE MOVEMENT OF THE SHOE RELATIVE TO THE CARRIER, AND A FLAT KEEPER-PLATE HOUSED IN SAID SLOTS AND EXTENDING BETWEEN THE SHOE AND CARRIER SLOTS TO MAINTAIN SAID SLOTS COPLANAR AND SAID SHOE AGAINST AXIAL DISPLACEMENT ALONG SAID AXIAL-EXTENDING SURFACES. 